The use of high-voltage, high-capacity positive electrodes in lithium-ion batteries is complicated by their tendency to degrade organic electrolyte solvents. Additionally, organic electrolyte solvents can have flammability issues, particularly when the batteries are subjected to excessive temperatures. Additives to improve thermal stability have been proposed for lithium batteries, as have flame resistant solvents. Various additives have been proposed that limit flame propagation or have flame retardant properties. Generally, these additives decrease the performance of the cell. The trade-off of the flame-suppressant properties interfere with the general operation of the battery, resulting in a poor overall product.
There is an ongoing need for advanced electrolyte solvents having one or more properties such as a large electrochemical stability window, a high ionic conductivity with a very low electronic conductivity, a low vapor pressure and low viscosity over a broad temperature range, and a lower flammability (e.g., due to a higher flash point) than conventional carbonate solvents. The solvents, electrolytes, electrochemical cells, batteries and methods described herein address this ongoing need.